This invention relates to a piston for producing a pressure surge in a wind tunnel, wherein the piston is propelled under the action of a gas pressure of at least 20 bars in a first passage from an initial position to a target surface so that a diaphragm disposed at the end of the first passage is torn under the compression produced by the approaching piston, and the resulting pressure surge is transmitted by a second passage, that is filled with a testing gas, to a thin sheet so that the latter is torn and the test gas flows as a supersonic shock wave into a testing chamber.